IADSPL : Other Synthesis Methods (page 28)

Other Synthesis Methods

There are a number of other synthesis methods including :

FM : Frequency Modulation (too complicated to deal with here).
Wavetable : single (usually) cycles of a complex waveform.
Sample playback : complete note.

Quick demo of sample playback synthesis :

		octave:1 > x= sndfile_load ('~/IADSPL/AudioFiles/pianoe2.wav');
		octave:2 > plot (x)
		octave:3 > audio_play (44100, x)
		octave:4 > audio_play (44100 * 2^(1/12), x)

Here we altered the sample rate and hence the playback speed to vary the pitch. In real sample playback synthesisers, they only use one sample rate and a DSP technique called Sample Rate Conversion is used to change the playback speed.

Extreme pitch shifts (ie playing a high note back very slowly to get a low note) can sound strange, so it is common to sample an instrument playing a number of different notes across its range and then sample rate convert the nearest note to get the desired note.